Field of the Invention
This invention relates to celestial navigation devices and more particularly relates to devices for lOcating the longitude on the earth of the user.
In the past, it has been customary to use a sextant to make the necessary readings for determining the longitude of a preselected location. There are, however, inherent disadvantages to the use of a sextant. Preferably, it is used with an ocean horizon, and thus, is much more difficult to use in locations where a horizon is not visible to the observer, and where trees and structures, such as houses and buildings obstruct the necessary view. Thus, using available devices and known methods presents difficulty in determining longitude, particularly at a location in the presence of obstacles which impair the view of the observer, and under some weather conditions such as when the horizon is obscured by clouds and the like.
It is a principal object of the invention to provide a new and improved device for determining the longitude of a particular location.
It is another object of the invention to provide a longitude finding device which does not require observation of an ocean horizon.
It is another object of the invention to provide a longitude finder which may be used where buildings, trees, and the like partially obscure the vision of the user.
It is another object of the invention to provide a longitude locating device which is usable so long as solar system bodies such on the north star and the moon or another identifiable planet due south of the observer are visible.
It is another object of the invention to provide apparatus and method for determining the longitude of a selected location comprising means and a method for simultaneously observing a first body such as the north star and a second body such as the moon or a planet due south of the observer, recording GMT (Greenwich mean time), and finding the GHA (Greenwich hour angle) for the second planet, the GHA being the same as the longitude of the observer.
It is another object of the invention to provide a longitude locating device employing a mirror and sight means for simultaneously observing a first body such as the north star and a selected planet due south of the observer.
It is another object of the invention to provide a longitude finder which includes reflective means and direct sight means for simultaneous viewing of the north star and a selected planet or the moon due south of the observer.
It is another object of the invention to provide a longitude finder which includes sight means for viewing the north star including and circular reflective glass means providing a double reflective image of the moon or planet due south of the observer.
In accordance with the invention, there is provided a longitude finder having means for directly sighting a first solar system body such as the north star, means for sighting a reflection of a second solar system body, such as the moon or a selected planet, south of the user, and means for aligning the image of the second body in a vertical line with the first body establishing the longitude of the second body. One form of the device includes a mirror with sight panels to line up the image with the directly sighted first body. Another form of the invention includes a reflective sphere providing a double image of the second body. The method of the invention includes sighting a first solar system body, sighting a reflected image of a second body due south of the first body, lining up the two images on a vertical line, determining the Greenwich mean time of the sighting, and determining the longitude of the second body at such Greenwich mean time.
The above objects and advantages of preferred embodiments of the invention will be better understood from the following detailed description thereof in conjunction with the accompanying drawing wherein: